Rotate a group of 6 objects to align 3 points (each on a different object) on a plane
Select all blocks and enter edit mode (TAB), change pivot point to active element.
 



then enter vertex select mode (number one on horizontal numbers on keyboard above Q)
Select all verts and click on one of the bottom verts so you have that one as active. Press 1 on number pad (right numbers). Use move tool (G) and right after press Z to move blocks down to where you want. Now while still in front view (that you set by pressing 1 on number pad) press R to rotate your blocks until one of the other 2 verts are aligned with the plain. Then switch to side view (number 3 on your number pad) and rotate again until 3rd vert is aligned